wild animals born with tameness required for domestication aren't born with the breed average stats like they should be.

breeding two ancestor animals via spawn egg, /summon command, or wild spawns, will produce domestic animals as it should but their stats will be that of the parents instead of the breed. ie; two Aurochs might make an Angus, but it won't be born with 3/4/3/1 as its stat spread.

leghorn from two wild-spawned junglefowl parents;

minecraft 1.16.5, hotchicks v.1.0.0, forge 1.16.5 36.2.39